Luby Transform codes are fountain codes that are used for encoding and decoding data in two-way communication. LT encoding lends itself to distributed implementation, and hence can be used to improve the communication efficiency by enabling parallel downloads from multiple mirror sites or disks. These days in order to achieve complete data recovery, LT codes are optimized by using various variation methodologies.
The generalization of LT codes helps in improving the data recovery. However, it is difficult to design the generalized LT codes for a large number of demand sets. Methods used for design of GLT codes require non-linear and often exhaustive search. Hence, the time-complexity for design can be high, leading to poor designs in several cases. Distributed LT codes have also been designed to address the sensitivity of LT codes towards the degree distribution. This has been achieved by selectively XOR-ing the symbols at the relay in order to create a statistical effect of construction an LT code on the concatenation of all source files. Although the methods results in reduction in download time, however it is limited to the cases where all sources have equal priority and all sinks have equal demands.
Other such methods towards design of LT codes have been proposed by A. Eryilmaz, A. Ozdaglar and M. Medard, ‘On the Delay and Throughput Gains of Coding in Unreliable Network’, Fragouli and E. Soljanin, ‘Network Coding Fundamentals’, M Luby, ‘LT codes’ and A. Shokrollahi, “Raptor Codes”.